TA access at the Artificial Pond and stream system of the Umweltbundesamt in 2018

Project title: Metformin Transformation in a Large Scale Artificial River System

Project acronym: TransMetProject duration: May to August 2018

Metformin is one of the most commonly prescribed antidiabetic pharmaceuticals on the global scale and recent studies indicate that metformin might cause endocrine disrupting effects in fish. It enters the waste water untransformed as it is no metabolised in humans. In addition, wastewater treatment plants are not designed to remove pharmaceuticals like metformin. Information on its fate in surface water under natural conditions is scare and known degradation rates are ranging between few and more than 100 days. The transformation products guanylurea and methylbiguanide were already detected in wastewater and surface water. The present project will study degradation and transformation processes as well as plant uptake of the highly polar drug metformin in an artificial river system. Therefore, metformin, guanylurea and methylbiguanide will be analysed in water, sediment and macrophytes.

Metformin uptake was shown in the macrophytes Phragmites australis and Typha latifolia. The latter is also able to degrade metformin to methylbiguanide. Uptake and degradation of metformin by macrophytes could allow for their use in phytoremediation. Furthermore, macrophytes accumulating metformin could present an additional exposure route for water organisms like fish and macrozoobenthos by feeding on the contaminated plant material. Hence, the potential of additional macrophytes, i.e. Typha angustifolia, Myriophyllum spicatum, Potamogeton natans, Ranunculus aquatilis and Sparganium sp. for bioaccumulation of metformin will be investigated.

The attenuation of organic micropollutants occurring in rivers is highly dependent on the hyporheic zone, i.e. the sediment region below and alongside the streambed. The hyporheic zone is a dynamic and complex transition region characterized by the simultaneous occurrence of multiple physical, biological and chemical processes. This is true not only for nutrient cycling and natural organic matter but also for organic micropollutants. Increased exchange between surface and pore water is expected to promote micropollutant degradation in river systems by bringing dissolved compounds in contact with biofilms. We therefore aim to identify and understand natural or artificial structures that promote this exchange and investigate the impacts of river bed morphology, microbial communities, biogeochemical conditions in the hyporheic zone on the degradation and transformation of metformin in the artificial stream.

To identify potential degradation hot spots in the sediment as potential driver of the long term degradation rates of metformin and formation of the potentially persistent transformation products guanylurea and methylbiguanide under controlled conditions, redox conditions, nutrient concentrations, oxygen profiles and stable tracers in the sediment will also be measured. Furthermore, the efficiency of sediment dune structures, macrophytes and artificial flow barriers in creating hyporheic flow and degradation hot spots will be compared as well as the interaction between microbial communities of the hyporheic zone, flow barriers and biogeochemical processes will be assessed.

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